Question

In this problem, how do you know which atoms or groups are going away, towards you, or in plane from the chiral center? for example, why do they assume that hydrogen is going away (dotted line) and Ch3 is coming towards you (bold colored line)? And how do you know which direction Ch2Ch2Br and Br is going in? its just a single line (Not dotted or bold). I know directions are important in determining R/S.

Ex: In the second photo for problem B, how do you know which groups are coming towards you or away so you could determine R/S?

опје іп, оон, NCH, natural (S)-alanine unnatural (R)-alanine SOLVED PROBLEM 5-2 Draw the enantiomers of 1,3-dibromobutane and label them as (R) and (S). (Making a model is particularly helpful for this type of problem.) CH-CH2-CH-CH, Br SOLUTION The third carbon atom in 1,3-dibromobutane is asymmetric. The bromine atom receives first priority, the (-CH CH Br) group second priority, the methyl group third, and the hydrogen fourth. The following mirror images are drawn with the hydrogen atom back, ready to assign (R) or (S) as shown. CH,CH,Br CH_CH_Br Не со HC Br (s) Br" CH, (R)